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Biomedical subjects

M Griffin

Publications and source records attributed to M Griffin.

At least 235 records · Page 13Linked to original sources
PubMed1986

Comparative study of the ability of three xanthobacter species to metabolize cycloalkanes.

The ability of three species of Xanthobacter to metabolize cyclohexane and its derivatives has been compared. Xanthobacter flavus was unable to utilize any of the cycloalkanes under investigation. X. autotrophicus was unable to utilize cyclohexane but was able to grow with a limited range of substituted cycloalkanes, including cyclohexanol and cyclohexanone. Comparison of a previously isolated cyclohexane growing Xanthobacter sp. with X. flavus and X. autotrophicus indicated it to be closely related to X. autotrophicus. Studies with cell-free extracts have indicated that the route of metabolism for cyclohexanol by X. autotrophicus is the same as that shown for the cyclohexane growing Xanthobacter sp., proceeding via cyclohexanol-->cyclohexanone--> epsilon-caprolactone-->--> adipic acid. A comparison of the cyclohexanol dehydrogenase found in X. autotrophicus with that found in the cyclohexane-growing Xanthobacter sp. indicated these enzymes to be distinctly different from one another on the basis of substrate specificity, molecular weight, and pH optima. The cyclohexanone monooxygenase enzymes found in the two bacteria were also found to be different when the pH optima and cofactor specificity of the two enzymes were compared. Preliminary genetic studies on the cyclohexane-growing Xanthobacter sp. have indicated that there are no plasmids present in this bacterium. The presence of RP4 in the Xanthobacter sp. can be detected following its conjugation with an RP4-carrying Escherichia coli strain.

Journal Article↗
PubMed1986

Chronic granulomatous disease presenting as an oculomucocutaneous syndrome mimicking Behçet's syndrome.

A female patient who presented for the first time at the age of 19 with oculomucocutaneous syndrome was found to have an absolute deficiency of neutrophil peroxide production. Neutrophil peroxide production as measured by chemiluminescence was zero on stimulation with opsonized zymosan. Direct membrane stimulation with FMLP and calcium ionophore also failed to elicit peroxide production. The diagnosis of chronic granulomatous disease should be considered in young patients with oculomucocutaneous syndrome.

Adult↗
PubMed1986

Marihuana smoking suppresses luteinizing hormone in women.

Smoking a single 1-g marihuana cigarette containing 1.8% delta 9-tetrahydrocannabinol induced a 30% suppression of plasma luteinizing hormone levels (P less than .02) in women during the luteal phase of the menstrual cycle. After marihuana placebo cigarette smoking, no luteinizing hormone suppression was observed in the same women under double-blind conditions. Marihuana may have adverse effects upon reproductive function during the luteal phase of the menstrual cycle as a consequence of gonadotropin inhibition.

Cannabis↗
PubMed1985

Activation of transglutaminase at calcium levels consistent with a role for this enzyme as a calcium receptor protein.

The sensitivity of tissue transglutaminase to activation by Ca2+ and other cellular factors was investigated using the enzyme purified from rat liver. The inclusion of Mg2+ in the assay system appeared to reduce the Ca2+-requirement of the enzyme when native N,N'-dimethylcasein was used as the protein acceptor substrate. However, when this protein was dephosphorylated, the Ca2+-requirement was unaffected by Mg2+. In addition, using this modified assay, a Km for Ca2+ was calculated to be in the range of 3-4 microM, at least an order of magnitude lower than that obtained with native acceptor substrate. Membrane phospholipids, 1,2-diolein and calmodulin were found not to affect the activation of transglutaminase by Ca2+. The sensitivity of transglutaminase to Ca2+ which we have now demonstrated suggests that this enzyme may directly act as a receptor protein for Ca2+ during stimulus-response coupling mediated by this cation.

Animals↗
PubMed1985

Alterations in the distribution and activity of transglutaminase during tumour growth and metastasis.

Transglutaminase activity and subcellular distribution have been examined in both normal and tumour tissue. Subcellular fractionation of rat liver demonstrated a bimodial distribution for transglutaminase between the particulate (approximately 40%) and cytosol (approximately 60%) fractions. Isolation of enriched plasma membrane fractions indicated the presence of membrane associated transglutaminase activity which co-distributed with that of 5'-nucleotidase and Na+/K+-ATPase. Induction of hepatocellular carcinomas in rats by treatment with either diethylnitrosamine or 6-p-dimethylaminophenylazobenzothiazole resulted in a reduction in transglutaminase activity which was accompanied by redistribution of the enzyme to the particulate fraction of the cell. The tumour bearing liver appeared to represent an intermediate stage between the hepatocellular carcinoma and control liver when assayed for content and distribution of transglutaminase activity. The transglutaminase activity of four transplantable rat sarcomas (P7, P8, MC3 and CC5) was found to be greatly reduced when compared with the normal tissues of rat liver, lung and spleen. A further reduction in this activity occurred in the primary growths of the sarcomas P7 and P8 following detection of metastases. Our data suggest that such changes in the distribution and content of transglutaminase may be a feature of tumour tissue and may be of value in both monitoring and investigating the carcinogenic process.

Acyltransferases↗
PubMed1985

Isolation and Characterization of a Cyclohexane-Metabolizing Xanthobacter sp.

An unusual Xanthobacter sp., capable of independent growth on cyclohexane as the sole source of carbon and energy, has been isolated from soil by using classical enrichment techniques. The mean generation time for growth on cyclohexane was 6 h. The microorganism showed a limited ability to utilize hydrocarbons, with only alicyclic hydrocarbons closely related to cyclohexane supporting growth. Ultrastructural studies indicated the presence of electron-transparent vesicles in the cyclohexane-grown Xanthobacter sp., but the presence of complex intracytoplasmic membranes could not be identified. A soluble inducible enzyme capable of oxidizing cyclohexane was identified in cell extracts. This enzyme had a pH optimum of 6.5, an absolute specificity for NADPH, and a stoichiometric requirement for molecular O(2) which was consistent with the formation of cyclohexanol. The enzyme showed no activity towards straight chain alkanes and only a limited activity towards unsaturated ring compounds. Enzymatic studies with cell extracts have indicated the main route of metabolism of cyclohexane by this Xanthobacter sp. to proceed via cyclohexane --> cyclohexanol --> cyclohexanone --> 1-oxa-2-oxocycloheptane (epsilon-caprolactone) --> 6-hydroxyhexanoate (6-hydroxycaproate) --> --> adipic acid. Alternative routes involving initial double hydroxylation of the cyclohexane ring may operate fortuituously but are unlikely to represent major pathways for the dissimilation of cyclohexane by this microorganism.

Journal Article↗
PubMed1985

Comparison of hand preference in trainable mentally handicapped and nonhandicapped children.

Hand preference was compared in 22 trainable mentally handicapped and 22 nonhandicapped children (Mage 78.00 mo.). Significant differences were found, showing the nonhandicapped group had a stronger preference when presented 10 hand-choice items from The Harris Tests of Lateral Dominance. In addition, stronger lefthandedness characterized the handicapped group, supporting previous research.

Child↗
PubMed1984

Clinical manifestations and descriptive epidemiology of Lyme disease in New Jersey, 1978 to 1982.

Clinical manifestations and epidemiologic characteristics of 117 cases (31 children and 86 adults) of Lyme disease in New Jersey from 1978 to 1982 are summarized. The male-female sex ratio was 1.9:1. An endemic focus in Monmouth County has been recognized. Erythema chronicum migrans was present in 93% of cases and was the only clinical manifestation in 25% of patients. Nonspecific febrile syndrome, in addition to erythema chronicum migrans, was present in 45% of cases; 26% had arthritis. The proportion of cases with arthritis in 1982 (7/56) was less than for 1978 to 1981 (24/61) probably because of better recognition of milder cases by physicians and earlier antibiotic treatment, which may have reduced late complications. Meningitis (10%) and cranial nerve palsies (8%) were the most frequent neurological manifestations. As medical personnel and the public become more aware of the disease, Lyme disease is being recognized with increased frequency in central and southern New Jersey.

Adolescent↗
PubMed1984

The inhibition of glucose-stimulated insulin secretion by primary amines. A role for transglutaminase in the secretory mechanism.

Rat pancreatic islets contain a Ca2+-activated and thiol-dependent transglutaminase (EC 2.3.2.13) comparable in activity with that found in rat liver, lung and spleen. The Ca2+-dependence of this enzyme is such that half-maximal velocity was obtained in the region of 40 microM. Preincubation of rat islets with primary-amine substrates of transglutaminase (monodansylcadaverine, methylamine, ethylamine, propylamine and cystamine) led to an inhibition of glucose-stimulated insulin release by these amines. Kinetic analysis of the competitive substrates methylamine, monodansylcadaverine, propylamine and ethylamine for their ability to inhibit islet transglutaminase activity indicated a potency that matched their ability to inhibit glucose-stimulated insulin release. When these amines were tested for their effects on glucose-stimulated protein synthesis and glucose utilization, the most potent inhibitor of insulin release, monodansylcadaverine, had no effect on either process at 100 microM. The amines cystamine, ethylamine, methylamine and propylamine had variable effects on these metabolic processes. For ethylamine, methylamine and propylamine, concentrations were found which inhibited glucose-stimulated insulin release in a manner which was found to be independent of their effects on either glucose oxidation or protein synthesis. Primary amines may therefore inhibit insulin release through their incorporation by islet transglutaminase into normal cross-linking sites. A role for protein cross-linking in the secretory mechanism is suggested.

Acyltransferases↗
PubMed1984

Detection of epsilon(gamma-glutamyl) lysine.

Detection of epsilon(gamma-glutamyl) lysine crosslinks is not only necessary for establishing the importance of the dipeptide as a post-translational modification of proteins, but provides information as to the importance of the transglutaminase enzyme in a biological system. The crosslink may be detected using both indirect and direct methodology. Indirect methods for its detection include measurement of 'masked lysines' within a protein, detection of polymer formation by gel-electrophoresis and the inhibition of crosslinking by the incorporation of small molecular weight amines into the substrate protein. Direct methods for the detection of epsilon(gamma-glutamyl) lysine require the actual isolation of the dipeptide following its release from the sample protein by exhaustive proteolytic digestion. Separation of the dipeptide from other components of the digest may be achieved by either ion-exchange chromatography or gel filtration and its qualitative identification achieved by techniques such as paper-electrophoresis or thin layer chromatography. Quantitative estimation of epsilon(gamma-glutamyl) lysine normally involves its further separation by ion-exchange chromatography and its post-column detection following derivatisation with ninhydrin. More recent techniques include pre-column derivatisation of the dipeptide with fluorogenic reagents such as sigma-pthalaldehyde and separation by reverse phase HPLC. With the recent advances in liquid chromatography resulting in the improved resolution of amino acids, increased sensitivity, rapid analysis times, and small sample sizes, it appears likely that direct quantitation of epsilon(gamma-glutamyl) lysine will be the preferred method for the future.

Acyltransferases↗
PubMed1984

A role for polyamines in stimulus-secretion coupling in the pancreatic beta-cell.

Measurement of the content of polyamines in pancreatic islets indicated that no significant change in their concentration took place during glucose-stimulated insulin release. The finding, together with the absence of any effect of alpha-difluoromethylornithine on glucose-stimulated insulin release suggested that rapid synthesis of polyamines is not involved in stimulus-secretion coupling in the beta-cell. The concentration of polyamines found in islets were high enough for them to act as substrates for the Ca2+-dependent islet transglutaminase during insulin release. This was further demonstrated by the ability of islet transglutaminase to incorporate [14C]putrescine into proteins from islet homogenates and by the demonstration of an increase in the covalent incorporation of [14C]putrescine into the proteins of intact islets following their challenge with glucose. Unlike monoamine substrates of transglutaminase, putrescine failed to effectively inhibit insulin release when its intracellular concentration was increased. A role for polyamines in the secretory process through their incorporation into islet proteins is suggested.

Acyltransferases↗
PubMed1983

How much evolutionary advantage does sex confer?

In discussing the long term advantage of sex, Crow and Kimura (1965) and Maynard Smith (1971) have argued that the advantage of a reproductive system allowing recombination (sex) is greatest for large populations. However the validity of this conclusion depends upon the model used for evolution. We propose two simple models: the bootstrap model, where the number of loci at which favourable mutations may take place remains constant over long time periods; and the environment-led model, where evolution is at a constant rate dictated by the environment (and does not depend on the organism's ability to evolve). While the bootstrap model leads to conclusions similar to those mentioned above, the conclusions for environment-led evolution are the opposite: as the size of the population decreases the advantage for sex increases.

Biological Evolution↗
PubMed1983

B-lymphocyte typing (HLA-DR, MT, MB) interlaboratory reproducibility.

Frozen lymphocytes from six persons were shipped, in three batches, from one location to 11 other participating laboratories for B-lymphocyte typing. The cells were received by the participating laboratories in a frozen state with one exception. Four of the 12 (including the host laboratory) used two-color fluorescence method, seven used nylon wool to isolate B-lymphocytes followed by cytotoxicity testing using trypan blue, and one laboratory used goat anti-human F(ab')2 to isolate B-lymphocytes for two cells and two-color fluorescence method for the other four cells. Reference antigen assignments of the various cells were essentially the consensus of the various laboratories and major departures from those assignments were considered errors. Twelve typing errors were seen in a total of 67 typings (for HLA-DR), i.e., an error rate of 17.9%. Four of the errors might have been due to the poor state of cells resulting from the participating laboratory storing the cells for over four weeks before testing. Six of the 12 laboratories were in agreement for all six cells and made no errors. Typing for MT antigens did not appear to be particularly reliable, but there was a good interlaboratory correlation for MB antigen assignments. The exercise has established the feasibility of conducting a cell exchange for B-lymphocyte typing over a fairly wide geographic area, and has shown that the overall error rate for HLA-DR antigen assignments is about three times the rate of HLA-AB typing.

B-Lymphocytes↗